The present invention relates to a hard disk apparatus and, more particularly, to a magnetic disk apparatus having a single logical hard disk drive (HDD) implemented by a plurality of HDDs or physical HDDs.
A plurality of physical HDDs constituting a single logical HDD appear as if it was a single physical HDD, as seen from a host system. The logical HDD has cylinder areas each assigned to a particular physical HDD. The physical HDDs are provided with serial numbers (#1, #2 and so forth) in the ascending order of the cylinder number of the logical HDD.
It has been customary for, e.g., a host system to perform a write/read test with the above conventional magnetic disk apparatus, diagnosing the writing and reading operation of the apparatus including a drive control system. The write/read test enhances the reliability of the apparatus. The prerequisite with the write/read test is that data stored in magnetic disks by the user be protected from damage ascribable to the test.
In the HDD, user cylinders are arranged from the outer circumference toward the inner circumference and allow user's data to be written therein, as desired; only the radially innermost cylinder is assigned to diagnosis. At the time of the above test, writing and reading is executed with the innermost or diagnosis cylinder so as not to disturb the data stored in the user cylinders.
However, the problem with the conventional magnetic disk apparatus is that when the diagnosis is effected on the diagnosis cylinder of the logical HDD, it is not effected on all the physical HDDs This is because only the radially innermost cylinder of the logical HDD is assigned to the diagnosis. Specifically, the diagnosis cylinder is allocated only to a particular physical HDD, but not allocated to the other physical HDDs.